Pulverizer



6, 1945. R L I 2,368,961

PULVERIZER Filed April 2, 1942 2 Sheets-Sheet l Fig 1 INV ENT OR.

Thomas H Arnold ATTORNEY Feb. 6, 1945. T. ARNOLD 2,368,961

PULVERIZER Filed April 2, 1942 '2 Sheets-Sheet 2 Fig.3

IIIIIIIIIIIIIIIIIIIIIIIIII INVENTOR BY 7770 Q5 HAZUOZd I ATTORNEYPatented Feb. 6, 1945 2,368,961 PULVERIZER Thomas H. Arnold, Cherubsco,Mexico, assignor to-The Babcock & Wilcox Company, Newark, .N. J., acorporation of New Jersey i Application April 2, 1942, Serial No.437,330

s Claims. (01. 241 61 I The present invention relates to theconstruction and operation of pulverizers of the type designed forpulverizing coal, cement materials and the like and in which thepulverizedmaterial is removed from the grinding zone of the pulverizerin suspension in a gaseous carrier mediiun;

The general object of my invention is the provision of a pulverizer' ofthe type described which is characterized by the high degree of finenessof -m the" pulverized material discharged and the relatively low powerconsumption of the 'pulverizer. A further and more specific object isthe provision of an improved rotary classifier construction andarrangement for a pulverizer of the type described which greatlycontributes to the fineness of the output.

--The various features of novelty which characterize my "invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,itsoperating advantages and specific objects attained by its use,reference should be had to theaccompanying drawings and descriptivematter in whichI have 111115:- trated and. described a preferredembodiment of my invention.

Of'the drawings:

Fig. 1 is a sectional elevation of a pulverizer constructed inaccordance with my invention;

Fig. 2 is an enlarged view of the classifier section of Fig. 1; and

Fig. 3 is a fragmentary plan view of the rotary classifier.

The pulverizer illustrated is of the general type disclosed and claimedin U. S. Patent 2,275,595, granted March 10, 1942, andas shown in Fig. 1comprises a substantially cylindrical housing it, the base of whichincludes the drive assembly for a vertical drive shaft II. The shaft IIhas a conical yoke I2 keyed on its upper end. The grinding parts of thepulverizer comprise a lower rotary grinding ring l3 carried on the lowerouter pension into the portion of segmental relief gate 23 in one partthereof. The pulverized material'leaving the outer edge of the lowergrinding ring is swept up by the high velocity air stream and carriedupwardly in susthe housing above the grinding zone.

The housing top is formed by the annular plate I! and a raisedcylindrical center section or turret 25 forming a cylindrical chamber 26as a continuation of the central opening in the plate I].

Ancpening 21 is formed in the top of the turret for the discharge ofmaterial-laden air. 1 During the passage of the material-laden airupwardly along the side walls of the housing some of the oversizeparticles separate from the air stream and drop back into the grindingzone. Before the material-laden air can enter the turret section it issubjected to the action of a rotary classifier symmetrically arrangedrelative to the outlet 21;. The rotary classifier is formed by upper andlower horizontally arranged annular plates 3! 'a'nd"32 respectively. Theplate 3| extends'beyondthe circumference of the plate 32 andQat'itsinner periphery has an uprising circular flange 33 which extendsinto-the opening in the top plate [1. "A circular serie of fan or impactblades 35 is symmetrically arranged in an inverted frusto-conicalformation between the plates 3! and 32. The classifier blades arepreferably of angular cross -section, as shown in Fig. 3, and welded attheirends to the plates 3| and 32. The angular blades have an angle ofapproximately 90 betweenitheir 'rangement oversize particles in the airstreamtend to collect in the blade'pockets and slide downwardly alongthe pocket to the plate 32 and 0 thus out of the path of the stream ofmaterialend of the yoke, a circular row of grinding balls l4 arranged ina track on the ring l3, and a spring pressed non-rotary uppercring l5carried on theball row. The .material to be pulverized is deliveredthrough a feed spout l6 opening through the top wall ll of thehousingadjacent laden air passing through the classifier.

The classifier is detachably mounted on a supporting structure carried.by the drive yoke [2. The classifier support 31 forms a downwardlytapering continuation of the opening in the plate 32 to receive oversizematerial dropping outof the classifier. The material deposits on the topof the drive shaft and on a support base plate 38 and is discharged fromthat area through slots between rectangular plates 39 as in .saidPaten't No. 2,275,595. The discharged-oversize particles are returned tothe grinding zone for further pulverization.

In operation the classifier blades give the material-laden' air stream aswirl as it passes into the turret chamber 26; This swirling actionthrows the coarse material towards the sides of the turret chamber andtends to produce eddy currents in the upper circumferential corner ofthe chamber which cause the coarse material to move downwardly in arelatively dense stream along the side wall of the chamber. In order toreduce the static pressure drop through the turret outlet 2?, a conemember 46 is positioned in the opening 2! so as to form an upwardlytapering entrance to the outlet 21. The cone 40 is vertically adjustablerelative to the turret section by means of supporting hangers 4|extending through the top Wall of the turret and externally adjustable.This arrangement of the cone aids in confining the eddy currents to theupper corner of the turret chamber.

The coarse particles descending along the sides of the turret wouldordinarily accumulate on the classifier top plate 3| and spill over intothe air stream leaving the inner side of the classifier and recirculatein the turret chamber or be carried out through the discharge outlet 21.accordance with myinvention the upper portion of the classifier isconstructed and arranged to receive any coarse material separated in theturret section and return the same to the grinding zone. As shown inFig. 2, the classifier upper plate 3| is'arranged slightly below andinwardly of the central opening inthe housingtop plate IT. A circularseries of angularly spaced symmetrically arranged bars 4 5 are mountedon the upper surface of the classifier plate 3! and welded thereon in aposition in which the inner end of each bar is the leading end and thebar is tangentially arranged relative to a circle of slightly smallerdiameter 1 than a the plate flange 33. A fiat annular seal plate 46 ismounted on the outer section'of the bars 45 in a position in which thecircumferential outer edge of the plate 46 has a slight clearancerelative to the top plate I! and the inner circumferential edge isspaced from the classifier top platefiange 33 leaving an annular opening4'! therebetween through which coarse materialfrom the turret chambercan drop onto the top'plate 3! and be forced outwardly therefrom whenthe classifier is in operation by the bladeaction of the obliquelyarranged bars 45. A centrifugal effect is thus imposed on the coarseparticles sufiicient to overcome the pressure differentialjthrough theclassifier. The circumferentially discharged material is, directeddownwardly by a frusto-conical plate 48 on the underside of the housingtop plate l1.

The 'coarse particles, separated in the turret chamber are, thusdirected towards the grinding zone of the I pulverizer,therebyincreasing the fineness of the output through the discharge cone40. The increased fineness of the output is demonstrated by test resultson a coal 'pulverizer of I the character described used in a cement,kiln direct firing pulverized coal system, before and after'theinstallation of a classifier construe tion and arrangement in accordancewith my in-- vention: 1 o

Original Present Fmeness installation arrangement Per cent Per centThrough'50 mesh 99. 95 100 Through 100 mesh.. 99. 52 99.94 Through 150mesh. 96. 44 99. 48 Through 200 mesh.. 85.14 95. 55 Through 325 mesh 74.88. 38

In the operation" of my invention the coarse material in efiect'isstripped from the circumference of the whirling stream of air andmaterial in the turret chamber. 'This separating action can bevaried byaltering the width of the bars 45 to thus alter the quantity of airandthis condition. A substantial increase in fineness of the pulverizeroutput is thus obtainable with the described construction andarrangement,

while at the same time the wear on the classifier top plate due tocoarse material accumulating and riding around thereon is substantiallyelimi- "hated.

changes may be made in the form of the apparatus and character of thecarrier medium disclosed without departing from the spirit of theinvention covered by the claims, and that certain features of theinvention may sometimes be used without a. corresponding use 'of otherfeatures. In the claims, the word air is intended to generically coveranygaseous carrier medium suitable for removing pulverized material inthemanner described. I

I claim: I

1. In a pulverizer comprising a housing enclosing grinding parts forminga grinding zone, means for delivering material to be pulverized to saidgrinding zone, means for. directing an air stream upwardly through saidgrinding zone to .sweepup pulverized material discharging therefrom, andanopening in'the top of said housing, the combination of a turretforming an upward continuation of said opening and having a dischargeoutlet, a rotary member symmetrically arranged at the lower end of saidhousing opening and having an annular plate Within the periphery of saidhousing opening, and means .onsaid plate for circumferentiallydischarging coarse particles separated in said plate.

2. In a pulverizer comprising a substantially cylindrical housingenclosing grinding parts forming a 'grindingzone, means for deliveringmaterial to be pulverized to said grinding zone, means for directing anair stream upwardly through said grinding zone tosweep up pulverized'material discharging therefrom, and an opening in the top of saidhousing, the combination of a cylindrical turret forming an upwardcontinuation of said opening and having a discharge outlet in the topthereof, a rotary classifier symmetrically arranged at the lower end andWithin the periphery of said housing opening and having upper and lowerannular plates, a circular series of impact'blades extending betweensaid plates, and means on the upper side of said upper classifier platefor defiecting coarse particles depositing on'said upper plate towardssaidgrinding zone. 7

3. Ina pulverizer comprising a housing 'enclosing grinding parts formingagrinding zone, means for'delivering material tobe pul erized to saidgrinding zone, means for directingan air stream upwardly through saidgrinding zone to sweep up pulverized materialdischarging therefrom, andan opening in the top of said housing, thecombination of a turretformingan upward continuationof said opening and having an air dischargeoutlet, a rotary classifier arranged within the periphery of saidhousing opening "and turret and depositing on said o f said housingopening.

ticles separated in said turret towardssaid grin mg zone, said upperplat and'said material directing means thereon having at least'astilostantial part thereof extending within the periphery a. In a'pulverizer comprising a closing grinding parts iorniing a grindingzone, means for delivering materi-al to be pulverized to said grindingnone, means for directing an air stream upwardly through said grindingzone to sweep up pulverized material discharging therefrom, and'anopening in the top of said housing, the combination of a cylindricalturret forming an upward continuation of said opening and having a fiattop plate with a central discharge outlet therein, a rotary classifiersymmetrically arranged at the lower end of said housing opening andhaving upper and lower annular plates, a circular series of impactblades extending between said plates, a conical member forming-adownwardly flaring extension of said turret outlet, and means on theupper plate of said classifier "for deflecting coarseparticles separatedin said turret and depositing on said upper plate towards said grindingzone.

5. In a pulverizer comprising a housing enclosing grinding parts forminga grinding zone, means for delivering material to be pulverized to saidgrinding zone, means for directing an air stream upwardly through saidgrinding zone to sweep up pulverized material discharging therefrom, anda central opening in the top of said housing, the combination of acylindrical turret forming an upward continuation of said opening andhaving a central discharge outlet in the top thereof, a rotaryclassifier symmetrically arranged at the lower end and within theperiphery of said housing opening and having upper and lower annularplates, a circular series of angular impact blades extending betweensaid plates, a conical member forming a downwardly flaring extension ofsaid turret outlet, and means on the upper plate of said classifier fordeflecting coarse particles separated in said turret towards saidgrinding zone including an upwardly extending flange on the innerperiphery of said upper plate and a series of obliquely extending barson the upper side of said upper plate.

6. In a pulverizer comprising a substantially cylindrical housingenclosing grinding parts including a vertical drive shaft, a lowergrinding ring operatively connected to said drive shaft, a non-rotaryupper grinding ring, and a circular row of rolling grinding elementsbetween said grinding rings, means for delivering material to bepulverized to the inner side of said row, means for directing an annularair stream upwardly past the outer side of said grinding parts to sweepup pulverized material discharging therefrom, and a central dischargeopening in the top of said housing, the combination of a cylindricalturret surrounding said opening and having an outlet in its top, arotary classifier below said housing opening and operatively connectedto said drive shaft, said classifier having upper and lower annularplates arranged within the periphery of said housing opening, a circularseries of angularly spaced blades extending between said plates, andmeans on the upper plate of said classifier for directing coarseseparated in said turret towardsrsaid housing grinding :zone.

1'7. In a pulverizer icompri'sing'a substantially cylindrica'i lipusingenclosing vgrinding parts inousing en- @5110 eluding :a *vre tic'aldrive shaft, a lower grinding ring'sop'erati ly connected to said driveshaft, warren-rota upper grinding ring, and a circular of rollinggrinding elements between said grinding rings, means for deliveringmaterial to ice-pulverized to the inner side of said row, means fordirecting an annular air stream upwardly past the outer side of saidgrinding parts to sweep up pulverized material discharging therefrom,panda central discharge opening in the top of said housing, thecombination or a cylindrical turret surrounding and forming acontinuation of said opening and having an outlet in its top, a rotaryclassifier below said housing opening and operatively connected to saiddrive shaft, said classifier having upper and lower annular plates, acircular series of blades extending,

between said plates, a conical member forming a downwardly flaringextension of said turret outlet, and means on the upper plate of saidclassifier for directing coarse particles separated in said turret anddepositing on said upper plate towards said housing grinding zone.

8. A rotary classifier adapted to rotate about a vertical axis andcomprising horizontally arranged upper and lower concentric annularplates, a circular series of angularly spaced blades extending betweensaid plates, and bars on the upper side of said upper plate arrangedsubstantially tangential to the inner circumference of said upper platewith their inner ends leading in the direction of rotation of said upperplate for outwardly deflecting separated material depositing on saidupper plate.

9. A rotary classified adapted to rotate about a vertical axis andcomprising horizontally arranged upper and lower concentric annularplates of different diameters, a circular series of angularly spacedblades extending between said plates in an inverted frusto-conicalformation, and bars on the upper side of said upper plate, arrangedsubstantially tangential to the inner circumference of said upper platewith their inner ends leading in the direction of rotation of said upperplate for outwardly deflecting separated material depositing on saidupper plate.

10. A rotary classifier adapted to rotate about a Vertical axis andcomprising horizontally arranged upper and lower concentric annularplates of different diameters, a circular series of angularly spacedblades extending between said plates in an inverted frusto-conicalformation, and means on the upper side of said upper plate for outwardlydeflecting material depositing on said upper plate including an upwardlyextending flange on the inner periphery of said upper plate andobliquely arranged bars secured to the upper side of said upper plate atthe outer side of said flange. I

11. A rotary classifier adapted to rotate about a'vertical axis andcomprising horizontally ar ranged upper and lower concentric annularplates of different diameters, and a circular series of angularly spacedimpact blades extending between said plates in an invertedfrusto-conical formation, said blades having a V-shaped transchargeopening-in its upper'end fora gas carand means on the upper side of saidclassifieri 10 plate for directing coarse particles separatedin saidturret and depositing on said plate into said housing; I

13. In combination, a housing having a circular discharge opening in itsupper end for a;-l5

gas carrying vparticles of finely divided material in suspension, a'cylindrical turret forming an upward continuation of said housingopening and having a' gas discharge outlet .in the top thereof; a rotaryclassifier symmetrically arranged relative to saidhousing opening andhaving an upper annular plate arranged within the periphery of saidhousing opening, a lower plate, a circular series of spaced bladesextending between said plates, and means on the upper side of said upperclassifier plate for directing coarse particles separated in said turretand depositing on said upper plate into said housing.

THOMAS H. ARNOLD.

